The treatment of a gas, either natural gas or refinery gas, generally comprises a dehydration step employed to avoid problems of hydrate formation and of corrosion during transportation. The treatment may also comprise a step of separating higher hydrocarbons, for example C2 to C5 (LPG) hydrocarbons by cooling so as to adjust the dew point of hydrocarbons in order to avoid condensation during transportation, or to recover a LPG fraction easier to upgrade than the treated gas. It is also necessary to adjust the content of acid gases, particularly of H.sub.2 S and CO.sub.2.
The steps of treatment are generally independent. According to the known techniques:
The dehydration may be performed by washing with a solvent which is mostly a glycol such as diethyleneglycol (DEG). This solvent must be regenerated by distillation.
The LPG separation is performed by cooling at a temperature which must be the lower as the desired LPD recovery rate is higher.
The deacidification is performed by washing with a physical solvent (for example polyethylene glycol dimethylether=PEGDME or propylene carbonate) or a chemical solvent (amine). This solvent must be regenerated by distillation. According to French patent application No. 2,550,956, the purification of natural gas may be performed by washing the gas with liquid methanol. Methanol absorbs the impurites and must then necessarily be regenerated by distillation. According to the published United States patent application Ser. No. B 421,383, a wet gas is washed with methanol to remove therefrom at least a part of its water. A water-methanol phase is recovered which must be regenerated by distillation. The regeneration of the solvent may be performed for example by the method disclosed in European patent application No. 0,053,424.